Autoantibodies against bactericidal/permeability-increasing protein (BPI) in children with acute pneumonia

Antineutrophil cytoplasmic antibodies directed against bactericidal/permeability-increasing protein (BPI), an inhibitor of a lipopolysaccharide of gram-negative bacteria, are a common feature of chronic neutrophilic inflammatory processes such as cystic fibrosis. We investigated whether serum and salivary anti-BPI autoantibodies also appear in the course of acute pneumonia in 24 otherwise healthy children. Nine (38%) and four (17%) patients had detectable serum anti-BPI immunoglobulin G (IgG) (> or =4 IU mL(-1)) and IgA (ratio> or =1.2), respectively, on the day of hospital admission (day 0). There was no increase in the rate of occurrence or the concentration of these antibodies in the convalescent sera obtained on day 30. The presence of anti-BPI IgG on admission did not correlate with inflammatory markers (peripheral white blood cell count, C-reactive protein) or temperature on admission. Also, salivary anti-BPI IgA, determined on days 0, 3-5 and 30, did not appear during the course of acute pneumonia. In summary, a substantial proportion of previously healthy children have pre-existing anti-BPI IgG autoantibodies. Acute neutrophilic infection, i.e. pneumonia, however, neither triggered the appearance of new antibodies nor boosted the concentrations of pre-existing ones. Thus, in typical acute pneumonia in children, autoantibodies directed against BPI may not have clinical significance.

Autoantibodies directed against bactericidal/permeability-increasing protein in patients with cystic fibrosis: association with microbial respiratory tract colonization

BACKGROUND: Cystic fibrosis (CF) is associated with the appearance of serum autoantibodies directed against bactericidal/permeability-increasing protein (BPI). OBJECTIVES: To determine the age-specific seroprevalence rates of anti-BPI-IgG and IgA in a population of patients with CF and to correlate anti-BPI antibody concentrations with microbial respiratory tract colonization and pulmonary function variables at the time of serum sampling and 6 years thereafter. METHODS: Determination of BPI antibodies of the IgG and IgA isotypes using a commercial enzyme-linked immunosorbent assay in sera of a CF serum bank of 1992; correlation of anti-BPI antibody concentrations with age, clinical score, pulmonary function variables in 1992 and 1998, total serum immunoglobulin isotype concentrations and respiratory tract colonization with Pseudomonas aeruginosa and Aspergillus spp. RESULTS: Seventy-one patients (age in 1992, 14.1 +/- 7.5 years) were studied. Reactivities for anti-BPI-IgG and IgA were found in 28 (39%) and 26 (37%) patients, respectively. The seroprevalence of anti-BPI-IgA, but not IgG, increased significantly with age. P. aeruginosa colonization was associated with elevated concentrations of anti-BPI-IgG (P = 0.003) and IgA (P = 0.037). There were significant negative correlations between pulmonary function variables (vital capacity, forced expiratory volume in 1 s) in 1992 and 1998, respectively, and concentrations of anti-BPI-IgG or IgA in a multiple regression analysis. Anti-BPI-IgG, but not IgA, remained significantly associated with P. aeruginosa colonization (P = 0.006) and with reduced vital capacity (P = 0.01) in 1998 after correction for total serum isotype concentration. CONCLUSIONS: Anti-BPI-IgG are strongly associated with concurrent P. aeruginosa colonization and with long term restrictive pulmonary function abnormalities.

Diagnostic approach to hypercalcemia: relevance of parathyroid hormone and parathyroid hormone-related protein measurements

Background: Parathyroid hormone (PTH) and parathyroid hormone-related protein (PTH-rP) are two potent hypercalcemic hormones that act on the same targets. Autonomous secretion of the former is involved in primary hyperparathyroidism (PHPT), whereas the latter is responsible for humoral hypercalcemia of malignancy (HHM). Methods: From 250 consecutive, hypercalcemic serum samples sent to our laboratory for assessment of intact PTH, we were able to obtain clinical information, as well as an additional plasma sample for PTH-rP measurement, in 134 patients. At the time of sampling, patients could be classified into seven groups: cancer without known bone metastases (CaNoMeta, n=36), cancer with bone metastases (CaMeta, n=9), no evidence of cancer (noEvCa, n=71), sarcoidosis (Sarc, n=3), end-stage renal disease (ESRD, n=12), vitamin D overdose (VIT-D, n=2), and hyperthyroidism (Thyr, n=1). Results: In the CaNoMeta group, 29/36 patients had elevated PTH-rP levels, 9/36 patients had inappropriately elevated PTH levels, and 5/36 had elevated levels of both hormones. In the CaMeta group, three of the nine patients had inappropriately elevated PTH levels, two of them with concomitantly elevated PTH-rP levels. In the NoEvCa group, 63/71 patients had an inappropriate elevation of PTH levels and were diagnosed as having PHPT. Four of the 71 patients had elevated levels of both PTH and PTH-rP; three of them were in poor health and died within a short period of time. All of the ESRD patients had very high PTH and normal PTH-rP levels, except for one woman with high PTH-rP and undetectable PTH levels; she died from what later turned out to be a recurrent bladder carcinoma. In the Sarc, Vit-D, and Thyr groups, both PTH and PTH-rP levels were normal. Conclusions: (1) Elevated PTH-rP levels are a common finding in cancer patients without bone metastases. Intact PTH, however, should always be measured in hypercalcemic patients with malignancy because concurrent primary hyperparathyroidism is not rare. (2) Primary hyperparathyroidism accounts for hypercalcemia in 90% of patients without evidence of cancer whose PTH-rP levels may also be found to be elevated in a few cases, even some with surgically demonstrated parathyroid adenoma.

PTH-related protein is released into the mother's bloodstream during location: evidence for beneficial effects on maternal calcium-phosphate metabolism

Recent studies have indicated that parathyroid hormone-related protein (PTHrP) may have important actions in lactation, affecting the mammary gland, and also calcium metabolism in the newborn and the mother. However, there are as yet no longitudinal studies to support the notion of an endocrine role of this peptide during nursing. We studied a group of 12 nursing mothers, mean age 32 years, after they had been nursing for an average of 7 weeks (B) and also 4 months after stopping nursing (A). It was assumed that changes occurring between A and B correspond to the effect of lactation. Blood was assayed for prolactin (PRL), PTHrP (two-site immunoradiometric assay with sheep antibody against PTHrP(1-40), and goat antibody against PTHrP(60-72), detection limit 0.3 pmol/l), intact PTH (iPTH), ionized calcium (Ca2+), 25-hydroxyvitamin D3 (25(OH)D3) and 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), alkaline phosphatase (alkP), as well as for creatinine (Cr), protein, phosphorus (P), and total calcium (Ca). Fasting 2-h urine samples were analyzed for Ca excretion (CaE) and renal phosphate threshold (TmP/GFR). PRL was significantly higher during lactation than after weaning (39 +/- 10 vs. 13 +/- 9 micrograms/l; p = 0.018) and so was PTHrP (2.8 +/- 0.35 vs. 0.52 +/- 0.04 pmol/l; p = 0.002), values during lactation being above the normal limit (1.3 pmol/l) in all 12 mothers. There was a significant correlation between PRL and PTHrP during lactation (r = 0.8, p = 0.002). Whole blood Ca2+ did not significantly change from A (1.20 +/- 0.02 mmol/l) to B (1.22 +/- 0.02, mmol/l), whereas total Ca corrected for protein (2.18 +/- 0.02 mmol/l) or uncorrected (2.18 +/- 0.02 mmol/l) significantly rose during lactation (2.31 +/- 0.02 mmol/l, p = 0.003 and 2.37 +/- 0.03 mmol/l, p = 0.002, respectively). Conversely, iPTH decreased during lactation (3.47 +/- 0.38 vs. 2.11 +/- 0.35 pmol/l, A vs. B, p = 0.02). Serum-levels of 25(OH)D3 and 1,25(OH)2D3 did not significantly change from A to B (23 +/- 2.3 vs. 24 +/- 1.9 ng/ml and 29.5 +/- 6.0 vs. 21.9 +/- 1.8 pg/ml, respectively). Both TmP/GFR and P were higher during lactation than after weaning (1.15 +/- 0.03 vs. 0.86 +/- 0.05 mmol/l GF, p = 0.003 and 1.25 +/- 0.03 vs. 0.96 +/- 0.05 mmol/l, p = 0.002, respectively) as was alkP (74.0 +/- 7.1 vs. 52.6 +/- 6.9 U/l, p = 0.003). CaE did not differ between A and B (0.015 +/- 0.003 vs. 0.017 +/- 0.003 mmol/l GF, A vs. B, NS). We conclude that lactation is accompanied by an increase in serum PRL. This is associated with a release of PTHrP into the maternal blood circulation. A rise in total plasma Ca ensues, probably in part by increased bone turnover as suggested by the elevation of alkP. PTH secretion falls, with a subsequent rise of TmP/GFR and plasma P despite high plasma levels of PTHrP.

Pharmacokinetics of GHB and detection window in Serum and Urine after single uptake of a low dose of GLB - an Experiment with two volunteers

During the last few years γ-hydroxybutyric acid (GHB) and γ-butyrolactone (GBL) have attracted much interest as recreational drugs and knock-out drops in drug-facilitated sexual assaults. This experiment aims at getting an insight into the pharmacokinetics of GHB after intake of GBL. Therefore Two volunteers took a single dose of 1.5 ml GBL, which had been spiked to a soft drink. Assuming that GBL was completely metabolized to GHB, the corresponding amount of GHB was 2.1 g. Blood and urine samples were collected 5 h and 24 h after ingestion, respectively. Additionally, hair samples (head hair and beard hair) were taken within four to five weeks after intake of GBL. Samples were analyzed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) after protein precipitation with acetonitrile. The following observations were made: spiked to a soft drink, GBL, which tastes very bitter, formed a liquid layer at the bottom of the glass, only disappearing when stirring. Both volunteers reported weak central effects after approximately 15 min, which disappeared completely half an hour later. Maximum concentrations of GHB in serum were measured after 20 min (95 µg/ml and 106 µg/ml). Already after 4-5 h the GHB concentrations in serum decreased below 1 µg/ml. In urine maximum GHB concentrations (140 µg/ml and 120 µg/ml) were measured after 1-2 h, and decreased to less than 1 µg/ml within 8-10 h. The Ratio of GHB in serum versus blood was 1.2 and 1.6

Aromatase deficiency caused by a novel P450arom gene mutation: impact of absent estrogen production on serum gonadotropin concentration in a boy.

We identified a new point mutation in the CYP19 gene responsible for aromatase (P450arom) deficiency in a 46,XY male infant with unremarkable clinical findings at birth. This boy is homozygote for a 1-bp (C) deletion in exon 5 of the aromatase gene causing a frame-shift mutation. The frame-shift results in a prematurely terminated protein that is inactive due to the absence of the functional regions of the enzyme. Aromatase deficiency was suspected prenatally because of the severe virilization of the mother during the early pregnancy, and the diagnosis was confirmed shortly after birth. Four weeks after birth, the baby boy showed extremely low levels of serum estrogens, but had a normal level of serum free testosterone; in comparison with the high serum concentration of androstenedione at birth, a striking decrease occurred by 4 weeks postnatally. We previously reported elevated basal and stimulated FSH levels in a female infant with aromatase deficiency in the first year of life. In contrast, in the male infant, basal FSH and peak FSH levels after standard GnRH stimulation tests were normal. This finding suggests that the contribution of estrogen to the hypothalamic-pituitary gonadotropin-gonadal feedback mechanism is different in boys and girls during infancy and early childhood. In normal girls, serum estradiol concentrations strongly correlate with circulating inhibin levels, and thus, low inhibin levels may contribute to the striking elevation of FSH in young girls with aromatase deficiency. In contrast, estradiol levels are physiologically about a 7-fold lower in boys than in girls, and serum inhibin levels remain elevated even though levels of FSH, LH, and testosterone are decreased.

Role played by serum, a biological cue, in the adherence of Enterococcus faecalis to extracellular matrix proteins, collagen, fibrinogen, and fibronectin.

BACKGROUND: Most previous studies have found that Enterococcus faecalis isolates do not show significant adherence to fibronectin and fibrinogen. METHODS: The influence of various conditions on E. faecalis adherence to extracellular matrix (ECM) proteins was evaluated using a radiolabeled-cell adherence assay. RESULTS: Among the conditions studied, growth in 40% horse serum (a biological cue with potential clinical relevance) elicited adherence of all 46 E. faecalis strains tested to fibronectin and fibrinogen but not to elastin; adherence levels were independent of strain source, and adherence was eliminated by treating cells with trypsin. As previously reported, serum also elicited adherence to collagen. Although prolonged exposure to serum during growth was needed for enhancement of adherence to fibrinogen, brief exposure (<5 >min) to serum had an immediate, although partial, enhancing effect on adherence to fibronectin and, to a lesser extent, collagen; pretreatment of bacteria with chloramphenicol did not decrease this enhanced adherence to fibronectin and collagen, indicating that protein synthesis is not required for the latter effect. CONCLUSION: Taken together, these data suggest that serum components may serve (1) as host environmental stimuli to induce the production of ECM protein-binding adhesin(s), as previously seen with collagen adherence, and also (2) as activators of adherence, perhaps by forming bridges between ECM proteins and adhesins.

Fatty acylated proteins and the protein kinase C signaling pathway

Numerous proteins in intracellular signaling pathways are known to be covalently modified by long chain fatty acids. The objective of this project was to identify potentially novel components of the protein kinase C signaling pathway by virtue of their fatty acylation. A 64 kDa palmitoylated protein (p64) was identified that became deacylated following stimulation of quiescent cells with serum, FGF, or PDBu, suggesting that stimulus-dependent deacylation might alter interactions between p64 and other membrane/cytoskeletal components. A myristoylated protein of 68 kDa observed during these studies was identified as the "80K" PKC substrate. This protein was acylated cotranslationally with myristate through an amide linkage. The majority of the 80K protein was tightly associated with the plasma membrane, with approximately 20% in the cytosol. Although phosphorylation of the membrane-bound and soluble forms of the protein was increased 6-fold in response to PDBu, no changes in the subcellular distribution or myristoylation of the protein were observed. A cDNA encoding the murine form of this protein was cloned, and its deduced amino acid sequence revealed the presence of an N-terminal myristoylation consensus and five potential sites for phosphorylation by PKC. A mutant in which the N-terminal glycine residue was changed to alanine was no longer a substrate for NMT and consequently lost its membrane-binding potential. However, its ability to be phosphorylated in response to purified growth factors and phorbol esters was unimpaired. These results indicate that the myristoylated N-terminus of the 80K protein is required for its association with the plasma membrane, and that the cytoplasmic form of the protein can be phosphorylated independently of the membrane-bound form. Mutants of PKC were constructed in which the regulatory domain was removed and replaced by the N-terminus of the 80K or Al proteins. Unexpectedly, both the myristoylated and nonmyristoylated fusion proteins were tightly associated with the nuclear envelope. Further deletion analyses mapped nuclear targeting signals to the hinge region and a portion of the catalytic domain of PKC, explaining the ability of PKC to be translocated to the nucleus in response to certain stimuli. ^

drp, A novel cell density regulated protein

Growing cells are continuously processing signals of all varieties and responding to these signals by changes in cellular gene expression. One signal that cells in close proximity relay to each other is cell-cell contact. Non-transformed cells respond to cell-cell contact by arrest of growth and entry into G$\sb0,$ a process known as contact inhibition. Transformed cells do not respond to contact inhibition and continue to grow to high cell density, forming foci when in cell culture and tumors in the living organism. The events surrounding the generation, transduction, and response to cellular contact are poorly understood. In the present study, a novel gene product, drp, is shown to be expressed at high levels in cultured cells at high cell density. This density regulated protein, drp, has an apparent molecular weight of 70 kDa. Northern analysis shows drp to be highly expressed in cardiac and skeletal muscle and least abundant in lung and kidney tissues. By homology to two independently derived sequence tagged sites (STSs) used in the human genome project, drp or a closely related sequence maps to human chromosome 12. Density-dependent increases in drp expression have been demonstrated in six different cell lines including NIH 3T3, Hela and a human teratocarcinoma cell line, PA-1. Cells exhibit increased drp expression both when they are plated at increasing concentrations per unit area, or plated at low density and allowed to grow naturally to higher cell density. Cells at high density can exhibit several phenotypes including growth arrest, accumulation of soluble factors in the media, and increased numbers of cell contacts. Growth arrest by serum starvation or TGF-$\beta$ treatment fails to produce an increase in drp expression. Similarly, treatment of low density cells with conditioned media from high density cells fails to elicit drp expression. These results argue that neither soluble factors accumulated or expressed at high density nor simple exit from the cell cycle is sufficient to produce an increase in drp expression. The expression of drp appears to be uniquely regulated by cell density alone. ^

Effects of externally supplied protein on root morphology and biomass allocation in Arabidopsis

Growth, morphogenesis and function of roots are influenced by the concentration and form of nutrients present in soils, including low molecular mass inorganicN(IN, ammonium, nitrate) and organicN(ON, e. g. amino acids). Proteins, ON of high molecular mass, are prevalent in soils but their possible effects on roots have received little attention. Here, we investigated how externally supplied protein of a size typical of soluble soil proteins influences root development of axenically grown Arabidopsis. Addition of low to intermediate concentrations of protein (bovine serum albumen, BSA) to IN-replete growth medium increased root dry weight, root length and thickness, and root hair length. Supply of higher BSA concentrations inhibited root development. These effects were independent of total N concentrations in the growth medium. The possible involvement of phytohormones was investigated using Arabidopsis with defective auxin (tir1-1 and axr2-1) and ethylene (ein2-1) responses. That no phenotype was observed suggests a signalling pathway is operating independent of auxin and ethylene responses. This study expands the knowledge on N form-explicit responses to demonstrate that ON of high molecular mass elicits specific responses.

Factors other than the glomerular filtration rate that determine the serum beta-2-microglobulin level.

BACKGROUND β2-microglobulin has been increasingly investigated as a diagnostic marker of kidney function and a prognostic marker of adverse outcomes. To date, non-renal determinants of β2-microglobulin levels have not been well described. Non-renal determinants are important for the interpretation and appraisal of the diagnostic and prognostic value of any endogenous kidney function marker. METHODS This cross-sectional analysis was performed within the framework of the www.seniorlabor.ch study, which includes subjectively healthy individuals aged ≥ 60 years. Factors known or suspected to have a non-renal association with kidney function markers were investigated for a non-renal association with serum β2-microglobulin. As a marker of kidney function, the Berlin Initiative Study equation 2 for the estimation of the estimated glomerular filtration rate (eGFR(BIS2)) in the elderly was employed. RESULTS A total of 1302 participants (714 females and 588 males) were enrolled in the study. The use of a multivariate regression model adjusting for age, gender and kidney function (eGFR(BIS2)) revealed age, male gender, and C-reactive protein level to be positively associated with β2-microglobulin levels. In addition, there was an inverse non-renal relationship between systolic blood pressure, total cholesterol and current smoking status. No association with markers of diabetes mellitus, body stature, nutritional risk, thyroid function or calcium and phosphate levels was observed. CONCLUSIONS Serum β2-microglobulin levels in elderly subjects are related to several non-renal factors. These non-renal factors are not congruent to those known from other markers (i.e. cystatin C and creatinine) and remind of classical cardiovascular risk factors.

Serum concentrations of 25-hydroxyvitamin D and immunoglobulins in an older Swiss cohort: results of the Senior Labor Study.

BACKGROUND Vitamin D and the components of humoral immunity play important roles in human health. Older people have lower 25-hydroxyvitamin D (25(OH)D) serum levels than younger adults. We aimed to determine the levels of 25(OH)D serum concentrations in healthy senior citizens and to study their relationship to the levels of components of humoral immunity. METHODS A total of 1,470 healthy Swiss men and women, 60 years or older, were recruited for this study. A total of 179 subjects dropped out of the study because of elevated serum concentrations of C-reactive protein. Fasting blood sera were analyzed for 25(OH)D with the high-performance liquid chromatography (HPLC) and for parathyroid hormone (PTH), immunoglobulins and complement C4 and C3 concentrations with immunoassays. The percentage of participants in each of the four 25(OH)D deficiency groups--severely deficient (<10 ng/ml), deficient (10 to 20), insufficient (21 to 29 ng/ml) and normal (>=30 ng/ml)--were statistically compared. The relationship of the major components of the humoral system and age with 25(OH)D levels was also assessed. RESULTS About 66% of the subjects had insufficient levels of 25(OH)D. Normal levels of 25(OH)D were found in 26.1% of the subjects of which 21% were males and 30.5% were females (total study population). Severely deficient levels of 25(OH)D were found in 7.98% of the total study population. Low levels of 25(OH)D were positively associated with IgG2 (P = 0.01) and with C4 (P = 0.02), yet were inversely related to levels of IgG1 and IgA (P < 0.05) and C3 (P = 0.01). Serum levels of total IgA, IgG, IgG2 and IgG4 peaked together with 25(OH)D during late summer. CONCLUSIONS Approximately two-thirds of the healthy, older Swiss population presented with Vitamin D insufficiency. The incremental shift in IgA and C3 levels might not necessarily reflect a deranged humoral immune defense; however, given the high prevalence of vitamin D deficiency, the importance of this condition in humoral immunity will be worth looking at more closely. This study supports the role of vitamin D in the competent immune system.

Correlation between serum total globulins and gamma globulins and their use to diagnose failure of passive transfer in foals.

Various assays have been used as an aid to diagnose failure of passive transfer (FPT) of immunoglobulins in neonatal foals, but often lack sensitivity as screening tests, or are time consuming to perform and impractical as confirmatory tests. The aim of the present study was to evaluate whether measurement of serum total globulins (TG; i.e. total protein minus albumin) can be used to estimate the electrophoretic gamma globulin (EGG) fraction in hospitalised neonatal foals with suspected FPT. Sample data from 56 foals were evaluated retrospectively. The coefficient of rank correlation was 0.84. The area under the curve of ROC analysis was 0.887, 0.922 and 0.930 for EGG concentrations <2 g/L, < 4 g/L and <8 g/L, respectively. Cut-offs for TG achieved ≥90% sensitivity for detecting EGG <2 g/L, < 4 g/L and <8 g/L, with negative predictive values of >97% and >94%, using prevalence of 15% and 30%, respectively. These results suggest that measurement of TG can be used as a guide to predicting EGG, provided that appropriate cut-off values are selected, and this technique could be a useful initial screening test for FPT in foals.

Comparative assessment of ELISAs using recombinant saposin-like protein 2 and recombinant cathepsin L-1 from Fasciola hepatica for the serodiagnosis of human Fasciolosis.

Two recombinant Fasciola hepatica antigens, saposin-like protein-2 (recSAP2) and cathepsin L-1 (recCL1), were assessed individually and in combination in enzyme-linked immunosorbent assays (ELISA) for the specific serodiagnosis of human fasciolosis in areas of low endemicity as encountered in Central Europe. Antibody detection was conducted using ProteinA/ProteinG (PAG) conjugated to alkaline phosphatase. Test characteristics as well as agreement with results from an ELISA using excretory-secretory products (FhES) from adult stage liver flukes was assessed by receiver operator characteristic (ROC) analysis, specificity, sensitivity, Youdens J and overall accuracy. Cross-reactivity was assessed using three different groups of serum samples from healthy individuals (n=20), patients with other parasitic infections (n=87) and patients with malignancies (n=121). The best combined diagnostic results for recombinant antigens were obtained using the recSAP2-ELISA (87% sensitivity, 99% specificity and 97% overall accuracy) employing the threshold (cut-off) to discriminate between positive and negative reactions that maximized Youdens J. The findings showed that recSAP2-ELISA can be used for the routine serodiagnosis of chronic fasciolosis in clinical laboratories; the use of the PAG-conjugate offers the opportunity to employ, for example, rabbit hyperimmune serum for the standardization of positive controls.

Butyrate increases intracellular calcium levels and enhances growth hormone release from rat anterior pituitary cells via the G-protein-coupled receptors GPR41 and 43

Butyrate is a short-chain fatty acid (SCFA) closely related to the ketone body ß-hydroxybutyrate (BHB), which is considered to be the major energy substrate during prolonged exercise or starvation. During fasting, serum growth hormone (GH) rises concomitantly with the accumulation of BHB and butyrate. Interactions between GH, ketone bodies and SCFA during the metabolic adaptation to fasting have been poorly investigated to date. In this study, we examined the effect of butyrate, an endogenous agonist for the two G-protein-coupled receptors (GPCR), GPR41 and 43, on non-stimulated and GH-releasing hormone (GHRH)-stimulated hGH secretion. Furthermore, we investigated the potential role of GPR41 and 43 on the generation of butyrate-induced intracellular Ca2+ signal and its ultimate impact on hGH secretion. To study this, wt-hGH was transfected into a rat pituitary tumour cell line stably expressing the human GHRH receptor. Treatment with butyrate promoted hGH synthesis and improved basal and GHRH-induced hGH-secretion. By acting through GPR41 and 43, butyrate enhanced intracellular free cytosolic Ca2+. Gene-specific silencing of these receptors led to a partial inhibition of the butyrate-induced intracellular Ca2+ rise resulting in a decrease of hGH secretion. This study suggests that butyrate is a metabolic intermediary, which contributes to the secretion and, therefore, to the metabolic actions of GH during fasting.